It is known that in any method of bulk material transportation and storage it is liable to get consolidated. This hinders its effective intake by any pneumatic transport methods during unloading. Therefore, when unloading a bulk material it is, as a rule, loosened and aerated to bring it in a fluidized state which is optimum for the pneumatic transportation.
For bulk material transportation a method is known to consist in that the mechanically pre-loosened material is aerated by an additional quantity of air supplied directly into the nozzle mouth.
A disadvantage of this method stems from the fact that the material transportation is intensified only in the accelerating portion of the nozzle. This can be effective only in combination with a mechanism, for example a worm feeder, used to supply the material from the suction zone to the zone of supply of the additional amount of aerating air, i.e., to the nozzle mouth. This complicates the construction of the pneumatic transport equipment and increases the cost of transportation.
A pneumatic transport installation for re-loading bulk materials from ships is known to comprise a sucking nozzle with a loosening means provided with an electric drive and a device for supplying air to the mouth of the sucking nozzle. This installation suffers from the same disadvantages as the above-mentioned method. In addition, the installation fails to provide an adequately efficient intake of material because the loosening performed mechanically by two rotable blades fails to secure a symmetrical feed of the material to the intake zone.
In another known method of unloading bulk materials from vessels, the material being unloaded is mechanically loosened and forced-aerated in the intake zone, i.e., under the taking means, the aerating air being supplied continuously in nondirectional flows. The mixture of the bulk material with air produced in the intake zone is sucked by the taking means, where a reduced pressure is maintained, and is transported by virtue of the air.
The device carrying this method into effect comprises a sucking nozzle communicated with a suction pump through a pipe line used as a means for transporting the material. The end of the sucking nozzle facing the material being unloaded has a bevelled edge, i.e., the plane of the inlet opening of the nozzle is at a certain angle to the horizontal plane so that the inlet opening of the nozzle is elliptical. A vertical hollow shaft driven by an electric motor and coupled with a pressure line is attached to the sucking nozzle on the size of the bevelled edge. The lower end of the shaft has a hollow disc rigidly installed thereon, which extends almost to the center of the inlet opening of the sucking nozzle. The disc is made of a porous cermet material. The lower extension of the hollow shaft protrudes into the disc so that the shaft interior and the disc interior are intercommunicated. The disc performs the function of both the loosening means and the aerator for the bulk material being unloaded.
The hollow shaft with the disc is rotated by a motor, and the disc loosens the material in the intake zone under the nozzle. In addition, air is supplied from the pressure line through the hollow shaft, said air emerging through the porous walls of the disc to aerate the material, thus producing a mixture of the material with the air. The material-and-air mixture is sucked by the nozzle and transported along the pipe line. The device has also a mechanism for moving the nozzle which provides the lowering of the nozzle as the material is unloaded, as well as the movement of the nozzle in other directions.
A disadvantage of the above method for unloading bulk materials and the device implementing this method consists in low efficiency of material intake due to low aerodynamic efficiency of the nozzle having a bevelled edge, as well as owing to non-uniform loosening and aeration of the material with respect to the longitudinal axis of the nozzle in the intake zone. This is accounted for by the fact that the porous disc performing the aeration and loosening covers only a portion of the inlet opening of the nozzle and the material under that part of the nozzle which is far from the disc is aerated and loosened worse than in the immediate vicinity of the disc. The non-symmetrical arrangement of the disc with respect to the sucking nozzle leads also to aeration of the material not only in the intake zone, but also in other zones where the intake is not performed, i.e. to losses of the aerating air. Said losses of the aerating air are also aggravated by the fact that the air is supplied through a porous disc in non-directional flows.
Moreover, the horizontal disc hampers the movement of the sucking nozzle into the material, especially when the material being unloaded is in the consolidated state.
The above disadvantages affect adversely the capacity of the material unloading and enhance the energy consumption for the unloading. Finally, such a constructional arrangement of the unloading device fails to provide its operational reliability and safety, especially when used in a bilge of the ship being unloaded, where there are metallic uprights, bulkheads, etc., since it has rotating elements, viz., the disc and the shaft, and current-conducting elements to supply voltage to the electric motor.